Multi-speed transmission with an engine start/stop enabler

ABSTRACT

A transmission includes an input member, an output member, a plurality of torque-transmitting mechanisms that are selectively engageable to establish at least four forward speed ratios and at least one reverse speed ratio between the input member and the output member, and one or more latches associated with one or more of the torque-transmitting mechanisms. The one or more latches engages the respective torque-transmitting mechanisms during or prior to a start event.

FIELD

The present invention relates to a multi-speed transmission having botha plurality of gear sets and torque-transmitting devices that areselectively engageable to achieve multiple gear ratios. Morespecifically, the present invention relates to a multi-speedtransmission that includes an engine start/stop enabler.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may or may not constitute priorart.

A typical multiple speed transmission uses a combination of a pluralityof torque transmitting mechanisms, planetary gear arrangements and fixedinterconnections to achieve a plurality of gear ratios. The number andphysical arrangement of the planetary gear sets, generally, are dictatedby packaging, cost and desired speed ratios.

While current transmissions achieve their intended purpose, the need fornew and improved transmission configurations which exhibit improvedperformance, especially from the standpoints of efficiency,responsiveness and smoothness and improved packaging, primarily reducedsize and weight, is essentially constant. Accordingly, there is a needfor an improved, cost-effective, compact multiple speed transmission.

SUMMARY

A transmission includes an input member, an output member, a pluralityof torque-transmitting mechanisms that are selectively engageable toestablish at least four forward speed ratios and at least one reversespeed ratio between the input member and the output member, and one ormore latches associated with one or more of the torque-transmittingmechanisms. The one or more latches engages the respectivetorque-transmitting mechanisms during or prior to a start event.

Further features, advantages, and areas of applicability will becomeapparent from the description provided herein. It should be understoodthat the description and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of the presentdisclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.The components in the figures are not necessarily to scale, emphasisinstead being placed upon illustrating the principles of the invention.Moreover, in the figures, like reference numerals designatecorresponding parts throughout the views. In the drawings:

FIG. 1 is a lever diagram of an example of the transmission inaccordance with the present invention;

FIG. 2 is a schematic representation of an example of the transmissionshown in FIG. 1 in accordance with the present invention;

FIG. 3 is a block diagram of the transmission shown with an enginestart/stop enabler; and

FIG. 4 is a truth table listing the engaged torque-transmittingmechanisms for selected torque ratios achieved by the transmission ofFIG. 2.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

At the outset, it should be appreciated that in the particular exampleprovided, the eight speed automatic transmission of the presentinvention has an arrangement of permanent mechanical connections betweenthe elements of the four planetary gear sets. These mechanicalconnections generically link or relate the transmission embodiments.More specifically, a first component or element of a first planetarygear set is permanently coupled to a first component or element of thesecond planetary gear set. A second component or element of the firstplanetary gear set is permanently coupled to a third component orelement of a fourth planetary gear set. A third component or element ofthe second planetary gear set is permanently coupled to a thirdcomponent or element of a third planetary gear set. A second componentor element of the third planetary gear set is permanently coupled to asecond component or element of the fourth planetary gear set.

Referring now to FIG. 1, an embodiment of an eight speed transmission 10for a motor vehicle is illustrated in a lever diagram format. A leverdiagram is a schematic representation of the components of a mechanicaldevice such as an automatic transmission. Each individual leverrepresents a planetary gear set wherein the three basic mechanicalcomponents of the planetary gear are each represented by a node.Therefore, a single lever contains three nodes: one for the sun gear,one for the planet gear carrier, and one for the ring gear. The relativelength between the nodes of each lever can be used to represent thering-to-sun ratio of each respective gear set. These lever ratios, inturn, are used to vary the gear ratios of the transmission in order toachieve an appropriate ratios and ratio progression. Mechanicalcouplings or interconnections between the nodes of the various planetarygear sets are illustrated by thin, horizontal lines andtorque-transmitting devices such as clutches and brakes are presented asinterleaved fingers. Further explanation of the format, purpose and useof lever diagrams can be found in SAE Paper 810102, “The Lever Analogy:A New Tool in Transmission Analysis” by Benford and Leising which ishereby fully incorporated by reference.

The transmission 10 includes an input shaft or member 12, a firstplanetary gear set 14 having three nodes: a first node 14A, a secondnode 14B and a third node 14C, a second planetary gear set 16 havingthree nodes: a first node 16A, a second node 16B and a third node 16C, athird planetary gear set 18 having three nodes: a first node 18A, asecond node 18B and a third node 18C, a fourth planetary gear set 20having three nodes: a first node 20A, a second node 20B and a third node20C and an output shaft or member 22.

The input member 12 is coupled to the second node 16A of the secondplanetary gear set 16. The first node 14A of the first planetary gearset 14 is coupled to the first node 16A of the second planetary gear set16. The second node 14B of the first planetary gear set 14 is coupled tothe third node 20C of the fourth planetary gear set 20. The third node16C of the second planetary gear set 16 is coupled to the first node 18Aof the third planetary gear set 18. The second node 18B of the thirdplanetary gear set 18 is coupled to the second node 20B of the fourthplanetary gear set 20. The output member 22 is coupled to the secondnode 20B of the fourth planetary gear set 20.

A first torque-transmitting mechanism 24 selectively connects the thirdnode 14C of the first planetary gear set 14 with a stationary element ortransmission housing 50. A second torque-transmitting mechanism 26selectively connects the first node 14A of the first planetary gear set14 with the transmission housing 50. A third torque-transmittingmechanism 28 selectively connects the input member 12 and the secondnode 16B of the second planetary gear set 16 with the first node 20A ofthe fourth planetary gear set 20. A fourth torque-transmitting mechanism30 selectively connects the third node 16C of the second planetary gearset 16 and the first node 18A of the third planetary gear set 18 withthe first node 20A of the fourth planetary gear set 20. A fifthtorque-transmitting mechanism 32 selectively connects the third node 18Cof the third planetary gear set 18 with the first node 20A of the fourthplanetary gear set 20A.

Referring now to FIG. 2, a stick diagram presents a schematic layout ofan example of the eight speed transmission 10 according to the presentinvention. In FIG. 2, the numbering from the lever diagram of FIG. 1 iscarried over. The clutches, brake and couplings are correspondinglypresented whereas the nodes of the planetary gear sets now appear ascomponents of planetary gear sets such as sun gears, ring gears, planetgears and planet gear carriers.

In an example of the present invention, a first planetary gear set 14 isa simple planetary gear set. More specifically, planetary gear set 14includes a sun gear member 14A, a ring gear member 14C and a carriermember 14B that rotatably supports a set of planet gears 14D (only oneshown). Sun gear member 14A is connected for common rotation with afirst shaft or interconnecting member 34. Ring gear member 14C isconnected for common rotation with a second shaft or interconnectingmember 36. Carrier member 14B is connected for common rotation with athird shaft or interconnecting member 38. The planet gears 14D areconfigured to intermesh with both the sun gear member 14A and the ringgear member 14C.

In another example of the present invention, a second planetary gear set16 is a simple planetary gear set. More specifically, planetary gear set16 includes a sun gear member 16A, a ring gear member 16C and a carriermember 16B that rotatably supports a set of planet gears 16D (only oneshown). Sun gear member 16A is connected for common rotation with thefirst shaft or interconnecting member 34. Ring gear member 16C isconnected for common rotation with a fourth shaft or interconnectingmember 40. Carrier member 16B is connected for common rotation with aninput shaft 12. The planet gears 16D are configured to intermesh withboth the sun gear member 16A and the ring gear member 16C.

In yet another example of the present invention, a third planetary gearset 18 is a simple planetary gear set. More specifically, planetary gearset 18 includes a sun gear member 18A, a ring gear member 18C and acarrier member 18B that rotatably supports a set of planet gears 18D(only one shown). Sun gear member 18A is connected for common rotationwith the fourth shaft or interconnecting member 40. Ring gear member 18Cis connected for common rotation with a fifth shaft or interconnectingmember 42. Carrier member 18B is connected for common rotation with asixth shaft or interconnecting member 44. The planet gears 18D areconfigured to intermesh with both the sun gear member 18A and the ringgear member 18C.

In yet another example of the present invention, a fourth planetary gearset 20 is a simple planetary gear set that includes a sun gear member20A, a ring gear member 20C and a carrier member 20B that rotatablysupports a set of planet gears 20D (only one shown). Sun gear member 20Ais connected for common rotation with a seventh shaft or interconnectingmember 46. Ring gear member 20C is connected for common rotation withthe third shaft or interconnecting member 38. Carrier member 20B isconnected for common rotation with the sixth shaft or interconnectingmember 44 and an output shaft 22. The planet gears 20D are configured tointermesh with both the sun gear member 20A and the ring gear member20C.

The input shaft or member 12 is preferably continuously connected to anengine or to a turbine of a torque converter or an electric motor. Theoutput shaft or member 22 is preferably continuously connected with afinal drive unit or transfer case (not shown).

The torque-transmitting mechanisms such as a first, second, third,fourth, and fifth clutches 24, 26, 28, 30, and 32 allow for selectiveinterconnection of the shafts or interconnecting members 34-46, membersof the planetary gear sets 14-20 and the housing 50. For example, thefirst clutch 24 is selectively engageable to connect the second shaft orinterconnecting member 36 with the stationary element, ground, or thetransmission housing 50. The second clutch 26 is selectively engageableto connect the first shaft or interconnecting member 34 with thestationary element, ground, or the transmission housing 50. The thirdclutch 28 is selectively engageable to connect the input shaft or member12 with the seventh shaft or interconnecting member 46. The fourthclutch 30 is selectively engageable to connect the fifth shaft orinterconnecting member 42 with the seventh shaft or interconnectingmember 46. The fifth clutch 32 is selectively engageable to connect thefourth interconnecting shaft or member 40 with the seventhinterconnecting shaft or member 46.

Referring now to FIGS. 2 and 4, the operation of the example of theeight speed transmission 10 will be described. It will be appreciatedthat transmission 10 is capable of transmitting torque from the inputshaft or member 12 to the output shaft or member 22 in at least eightforward speed states or torque ratios and at least one reverse speedstate or torque ratio. Each forward and reverse speed state or torqueratio is attained by engagement of one or more of thetorque-transmitting mechanisms (i.e. first, second, third, fourth, andfifth clutches 24, 26, 28, 30, 32), as will be explained below. FIG. 4is a truth table presenting the various combinations oftorque-transmitting mechanisms that are activated or engaged X toachieve the various gear states.

For example, to establish reverse gear state R, the first clutch 24 isengaged or activated X and the second and fourth clutches 26 and 30 areengaged or activated X. The first clutch 24 in the engaged mode connectsthe second shaft or interconnecting member 36 with the stationaryelement, ground, or the transmission housing 50. The second clutch 26connects the first shaft or interconnecting member 34 with thestationary element or transmission housing 50. The fourth clutch 30connects the fifth shaft or interconnecting member 42 with the seventhshaft or interconnecting member 46.

To establish the first gear state 1^(st), the first, second, and thirdclutches 24, 26, 28 are engaged or activated X. The first clutch 24connects the second shaft or interconnecting member 36 and thestationary element or transmission housing 50. The second clutch 26connects the first shaft or interconnecting member 34 with thestationary element or the transmission housing 50. The third clutch 28connects the input shaft or member 12 with the seventh shaft orinterconnecting member 46.

To establish the second gear state 2^(nd), the first, second, and fifthclutches 24, 26, and 32 are engaged or activated X. The first clutch 24connects the second shaft or interconnecting member 36 and thestationary element or transmission housing 50. The second clutch 26connects the first shaft or interconnecting member 34 with thestationary element or the transmission housing 50. The fifth clutch 32connects the fourth shaft or interconnecting member 40 with the seventhshaft or interconnecting member 46.

To establish the sixth gear state 6^(th), the first clutch 24 isdisengaged and the third, fourth, and fifth clutches 28, 30, 32 areengaged or activated X. The clutch 24 in the disengaged mode acts as atraditional one-way clutch between the second shaft or interconnectingmember 36 and the stationary element or transmission housing 50. Thethird clutch 28 connects the input shaft or member 12 with the seventhshaft or interconnecting member 46. The fourth clutch 30 connects thefifth shaft or interconnecting member 42 with the seventh shaft orinterconnecting member 46. The fifth clutch 32 connects the fourth shaftor interconnecting member 40 with the seventh shaft or interconnectingmember 46. Likewise, the eight forward speed states are achieved throughdifferent combinations of clutch engagement, as shown in FIG. 5.

With further reference to FIG. 3, the transmission 10 includes an enginestart/stop enabler with a latch 72 associated with the second clutch 26and a pair of latches 74 and 76 associated with the first clutch 24. Thetransmission also includes a hydraulic control system 59 with a firstvariable force solenoid 64, a second variable force solenoid 66, a thirdvariable force solenoid 60, a fourth variable force solenoid 62, a fifthvariable force solenoid 70, and a sixth variable force solenoid 68. Inthe particular arrangement shown in FIG. 3, the first clutch 24 is incommunication with the first and the second variable force solenoids 64and 66. The second clutch 26 is in communication with the third variableforce solenoid 60. The third clutch 28 is in communication with thefourth variable force solenoid 62. The fourth clutch 30 is incommunication with the fifth variable force solenoid 70, and the fifthclutch 32 is in communication with the sixth variable force solenoid 68.Although the first clutch 24 is associated with a pair of latches and arespective pair of variable force solenoids, in some arrangements, asingle latch and a single variable force solenoid are associated withthe first clutch 24.

Note further that other hydraulic control systems can be used in certaintypes of arrangements. For example, in various arrangements, thehydraulic control system 59 includes, for example, variable bleedsolenoids or on/off devices or any other suitable devices to selectivelyengage the torque transmitting mechanisms 60, 62, 64, 66, 68, and 70 byselectively communicating hydraulic fluid to the various torquetransmitting mechanisms.

The variable force solenoids communicate in turn with the transmissionpump or an accumulator 80 or auxiliary pump and receive instructionsfrom a controller 90. The controller 90 can be associated with the motorvehicle's engine, transmission, or hybrid control module.

When the motor vehicle comes to a stop, the motor vehicle typicallystarts again in first, second, or reverse gear. That is clutches 24, 26,and 30 are engaged for reverse gear; clutches 24, 26, and 28 are engagedfor first gear; or clutches 24, 26, and 32 are engaged for second gear.So that the motor vehicle is ready to start again, the transmissionspump is generally sized to pump sufficient pressure to the clutches 24,26, 28, 30, and 32 after a vehicle stop so that the clutches 24 and 26and one of the clutches 28, 30, and 32 can be readily engaged when thevehicle starts again when the latches 72, 74, and 76 are not employed.Alternatively, the accumulator 80 is sized to provide sufficient fluidvolume and flow, as moderated by respective variable force solenoids 60,62, 64, 66, 68, and 70, to the clutches 24 and 26 and one of theclutches 28, 30, and 32. Alternatively, an auxiliary pump can beemployed in place of the accumulator to provide the appropriatehydraulic fluid pressure to the devices in the hydraulic control system59 to selectively engage the torque transmitting mechanisms 24, 26, 28,30, and 32. In some arrangements a combination of two or all of thetransmission pump, the accumulator 80, and the auxiliary pump providesflow to the torque transmitting mechanisms.

With the implementation of the latches 72, 74, and 76, which can bemechanical latches or hydraulic latches or any other suitable mechanismand which can be under the control of the controller 90, the clutches 24and 26 can be considered holding clutches. That is prior to or at astart event, the latches 72, 74, and 76 are activated to engage theclutches 24 and 26. As such, the transmissions pump or the accumulator80 or auxiliary pump only has to provide sufficient pressure orsufficient volume to engage one of the clutches 28, 30, and 32 forfirst, reverse, or second gear. In sum, with the use of the latches 72,74, and 76, the transmission pump or the accumulator 80 or auxiliarypump is sized to provide pressure or fluid volume for one clutch for astart event, whereas without the latches 72, 74, and 76, thetransmission pump or the accumulator 80 or auxiliary pump is sized toprovide pressure or fluid volume for three clutches for a start event.

Note that the use of the latches 72, 74, and 76 are not limited to eightspeed transmissions. The latches can be implemented into transmissionswith fewer speeds, such as, for example, transmissions with four, five,six, or seven forward speeds (both rear-wheel and front-wheel drive).Moreover, the latches can be implemented into transmissions with morethan eight speeds, such as, for example, transmissions with nine, ten,or more forward speeds.

The description of the invention is merely exemplary in nature andvariations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

What is claimed is:
 1. A transmission comprising: an input member; anoutput member; first, second, third and fourth planetary gear sets eachhaving first, second and third members; a plurality oftorque-transmitting mechanisms, a first torque-transmitting mechanism ofthe plurity of torque-transmitting mechanisms being selectivelyengageable to interconnect the first member of the first planetary gearset to a stationary member and a second torque-transmitting mechanism ofthe plurality of torque-transmitting mechanisms being selectivelyengageable to interconnect the third member of the first planetary gearset to the stationary member, the plurality of torque-transmittingmechanisms being engageable to establish at least four forward speedratios and at least one reverse speed ratio between the input member andthe output member; and one or more latches associated with one or moreof the torque-transmitting mechanisms, wherein the one or more latchesengages the respective torque-transmitting mechanisms during or prior toa start event.
 2. The transmission of claim 1 wherein the one or morelatches are hydraulic latches.
 3. The transmission of claim 1 whereinthe one or more latches are mechanical latches.
 4. The transmission ofclaim 1 wherein the one or more latches are two latches.
 5. Thetransmission of claim 1 wherein the one or more latches are threelatches.
 6. The transmission of claim 1 wherein the one or more latchesengages one or more of the torque transmitting mechanisms and a secondor third torque transmitting mechanism is engaged by increasing fluidpressure to the respective torque transmitting mechanism.
 7. Thetransmission of claim 1 wherein the one or more latches engages one ormore of the torque transmitting mechanisms and a second or third torquetransmitting mechanism is engaged by increasing a fluid volume to therespective torque transmitting mechanism.
 8. The transmission of claim 7wherein the torque transmitting mechanisms communicate with a hydrauliccontrol system that moderates the volume flow to the torque transmittingmechanisms.
 9. The transmission of claim 8 further comprising atransmission pump, an accumulator, or an auxiliary pump or a combinationthereof that provides flow to the torque transmitting mechanisms duringor prior to the start event.
 10. The transmission of claim 8 wherein thehydraulic control system receives instructions from a controller. 11.The transmission of claim 1 wherein the plurality of torque transmittingmechanisms is five torque transmitting mechanisms and wherein a third ofthe five torque transmitting mechanisms is engaged to establish areverse gear.
 12. The transmission of claim 1 wherein the plurality oftorque transmitting mechanisms is five torque transmitting mechanismsand wherein a third of the five torque transmitting mechanisms isengaged to establish a first gear.
 13. The transmission of claim 1wherein the plurality of torque transmitting mechanisms is five torquetransmitting mechanisms and wherein a third of the five torquetransmitting mechanisms is engaged to establish a second gear.
 14. Thetransmission of claim 1 wherein the plurality of torque-transmittingmechanisms are selectively engageable in combinations of at least threeto establish at least four forward speed ratios and at least one reversespeed ratio between the input member and the output member.
 15. Atransmission comprising: an input member; an output member; first,second, third and fourth planetary gear sets each having first, secondand third members; a plurality of torque-transmitting mechanisms, afirst torque-transmitting mechanism of the plurality oftorque-transmitting mechanisms being selectively engageable tointerconnect the first member of the first planetary gear set to astationary member and a second torque-transmitting mechanism of theplurality of torque-transmitting mechanisms being selectively engageableto interconnect the third member of the first planetary gear seat to thestationary member, the plurality of torque-transmitting mechanisms beingselectively engageable to establish at least eight forward speed ratiosand at least one reverse speed ratio between the input member and theoutput member; a plurality of latches associated with two of thetorque-transmitting mechanisms, wherein the plurality of latches engagesthe respective torque-transmitting mechanisms during or prior to a startevent; a plurality of variable force solenoids, at least one of theplurality of variable force solenoids being in communication with arespective force-transmitting mechanism to moderate the fluid volume tothe torque transmitting mechanism; and a controller that providesinstructions to the plurality of variable force solenoids.
 16. Thetransmission of claim 15 wherein the plurality of latches is twolatches.
 17. The transmission of claim 15 wherein the plurality oflatches is three latches.
 18. The transmission of claim 15 wherein theplurality of torque transmitting mechanisms is five torque transmittingmechanisms and wherein a third of the five torque transmittingmechanisms is engaged to establish a reverse gear.
 19. The transmissionof claim 15 wherein the plurality of torque transmitting mechanisms isfive torque transmitting mechanisms and wherein a third of the fivetorque transmitting mechanisms is engaged to establish a first gear. 20.The transmission of claim 15 wherein the plurality of torquetransmitting mechanisms is five torque transmitting mechanisms andwherein a third of the five torque transmitting mechanisms is engaged toestablish a second gear.